Tension control system



Sept. 9, 1952 A w, SEAR TENSION CONTROL SYSTEM Filed 001;. 30, 1945 sSheets-Sheet 1 Invehborr Arthur W. Sear, 135% 3% H is Atbcrne g.

P 9, 1952 A. w. SEAR 2,609,998

TENSION CONTROL SYSTEM Filed 001;. 30, 1945 5 Sheets-Sheet 2 Fig.2.

Inventor: Arthur W Sear,

His Attorne s.

Patented Sept. 9, 1952 TENSION CONTROL SYSTEM Arthur W. Sear, Stratford,Conn assignor to General Electric Company, a corporation of New YorkApplication October 30, 1945, Serial No. 625,504

17 Claims. 1

My invention relates generally to tension control systems for travelingstrip material such as wire, tape, and the like. More particularly, theinvention relates to wire driving and reeling mechanisms for magneticwire recording apparatus and the like, and has for its object theprovision of an improved system and apparatus for maintainingsubstantially constant wire speed and tension.

The recording medium commonly used in magnetic wire recording apparatusis a slender wire of suitable magnetizable material approximately 4 milsin diameter. This fragile wire is generally drawn through the recordingunit at speeds up to approximately 6 feet per second. It will thereforebe evident that, in order to prevent breakage. of the wire, it isnecessary accurately to control its tension. In some recording units nowin use the take-up spool is driven at approxi mately a uniform speed sothat, as the wire builds up on the take-up spool, the linear speed ofthe wire through the recording head increases. This slow variation inspeed does not ordinarily affect the fidelity of reproduction, since thewire is usually run through the apparatus in the same direction inreproducing operation as in recording operation. If, however, the wireis cut; so that a portion of the wire upon which a recording was made atone limit of winding of the take-up spool is played back with thetake-up spool near its opposite limit of winding, the difference betweenrecording and reproducing speeds will have an undesirable effect uponthe reproduction.

A more pronounced disadvantage of the takeup reel drive is that, as thewire builds up, its surface becomes somewhat uneven. The uneven surfacecauses irregular motion of the wire which results in sudden speedchanges or Wow" in reproduction. It will therefore be evident that, forfidelity of reproduction, it is desirable to run the wire at apredetermined fixed linear speed at all times. Moreover to preventbreakage of the wire, and to prevent wire slippage where a capstan driveis used, it is desirable that the tension be maintained substantiallyconstant.

Accordingly, it is a general object of my invention to provide animproved tension control system for strip material winding and reelingapparatus.

Still another object of my invention is the provision of constanttension driving means for a reversible strip winding apparatus or thelike.

It is a further object of my invention to provide constant linear speeddriving means for strip material winding and reeling apparatus.

It is a more particular object of the invention to provide an improvedwire driving apparatus It is a still further object of my invention tominimize wow in magnetic recording and reproducing apparatus and thelike.

It is a specific object of my invention to provide a readily reversibleconstant speed and constant tension wire driving apparatus for magneticwire recording equipment and the like.

In accordance with a preferred embodiment of my invention, a constantspeed driving pulley or capstanintermediate the supply and takeup reelsis arranged to drive the wire at a substantially constant linearspeed'independent of the reel speeds. The reels themselves are bothdriven in the direction of travel of the wire through separate variabletransmission elements from a common friction driving disk. The reelspeeds are controlled to maintain the wire tension substantiallyconstant by providing between the capstan and each reel a dancer pulleyarranged to control the driving ratio of the transmission elementassociated with the adjacent reel. Each variable transmission comprisesa friction spool connected to transmit power from a driving disk to adriven disk. The spool is mounted upon a linkage permitting axialmovement of the spool to control the speed ratio between the disks; andthe linkage is so arranged that a damping function is introduced intothe motion of the spool, thereby to minimize hunting of the apparatus.

My invention itself, along with further objects and advantages thereof,will be fully appreciated by referring now to the following detailedspecification taken in conjunction with the accompanying drawings, inwhich Fig. 1 is an exploded perspective view of a magnetic recordingapparatus embodying my invention; Fig. 2 is a plan View of the frontpanel of the apparatus shown at Fig. 1; Fig. 3 is a schematic linediagram showing the transmission linkage of Fig. 1 in elevation; Fig. 4is a vector diagram of velocity illustrating the theory of operation ofa single friction transmission element; Fig. 5 is a schematic diagram ofa single transmission element embodying my invention in another form;and Fig. 6 is a front elevation of still another transmission linkageembodying my invention.

At Fig. 2 I have indicated schematically the layout of the front panelof a magnetic recording apparatus embodying my invention. As indicatedin this figure, a traveling magnetic recording medium, such as a wire I,is passed between a pair of spaced reels 2 and 3 through a magneticrecording head 4 and an erasing head 5. In passing between the reels,the. wire 5 passes over a driven capstan 6 intermediate the reels, apair of dancer pulleys l and 8 on opposite sides of the capstan, and apair of level winding idler pulleys 9 and I0 intermediate the danc 3 erpulleys 1 and 8 and the reels 2 and 3, respectively. 'I'havealsoshownmounted upon the panel a controlswitch H and a reversing lever l2.

Referring now to Fig. 1, I have shown therein a perspective view of theapparatus with the panel removed. Driving power is obtained from areversible electric motor Id controlled by the line switch H and areversing switch Hi. The switch l4 connected by a suitable linkage IE toa reversing shaft l2a connected to the reversing lever 12. A frictionroller Iii-mounted upon the shaft of the motor [3 drives a disk I!mounted upon a shaft IS. The disk I1 is preferably of appreciable mass,sothat by its flywheel effect it aids in stabilizing the wire speed. Thewire driving capstan '6- is-mounted .upon the opposite end of the shaftl8.

Themotorlsalso drivesboth reels'ii and t in the direction-in whichthewire is traveling and at suchspeeds that. the wire tension forcesadjacent each. reel .are maintained substantially constantand equal. Forthis purpose, the shaft 18 is providedwithapulley 19 connected through abelt 20 to drive a pulley 2| mounted upon a shaft 22paralle1 to theshaft I8. The shaft 22 carries a friction drivingdisk23. The disk 23 isconnected by separatelyvariable friction transmission mechanisms 24and-25 to drive a pair of driven friction disks 26 and2'l, respectively.The

.disks 26 and 21-. are disposed; in the same plane asthe disk 23 and:are. mounted upon shafts 28 and.29. respectively. The shafts.28 and 29are parallel to the shaft I8 and carryat their opposite ends the reels-2and 3,- respectively.

The transmission'elementsl i and 25 are of similar construction and eachcomprises a pair of parallel jackshafts30, 3| .mounted in quills 32 and33, respectively,and'carrying at opposite ends friction rollersengagingthe disk 23 and one of the disks .26 01x21. Referring specifically tothe transmission element 25,-the jackshaft 36 carries at opposite ends apair of friction rollers 34 and 35, while the jackshaft 3! carries asimilar pair of'friction rollers 36 and 3'9. The rollers 34- and 35onthe shaft '30 are in lateral alignmentwith the rol1ers'36 and 31,respectively, on the shaft-3|. The rollers 34 and 36 engage the drivingdisk-23 and the rollers 35 and-3T engage the drivendisk 21. The quills-32 and 33 are connected together by a plate 3B fixedly connected to thequill 33 and having a pin and slot connection with the quill 32. Thequills 32 and-33 are positioned on opposite sides of the disks 23 and 21and are biased toward each other to bring the rollers-into engagementwith opposite sides of the disks. Biasing of the quills is accomplishedby means of a tension spring39 connected between the quills.

The transmission mechanism .25 is mounted upon a pair of links 40 and4|, the upper ends of which are pivotally connected to opposite ends ofthe quill 32. Similarly, the transmission mechanism .24 is mountedupon apair of links 42 and 43. Thelower ends of the links 49 and 42, whichwill be referred to hereinafter as control links. are pivotallyconnected to rocker arms 44 and 45, respectively. The rocker arms 44, 45are mounted upon fixed pivot pins 45 and 41', respectively. The lowerends of the links All and 43, which will be referred to hereinafter asdamping links, are connected to pins 48 and 49, respectively, which areslidably mounted in arcuate slots and 5|, respectively, in a fixed panel52. The pins 48 and 49 are connected together by a shift 4 bar 53, andthe pin 48 is provided with an ex tension: 54 engaging a slotone endgofa rocker arm 55. The rockeraarmi55 is mounted upon a fixed pivot 56 withits other end in pin and slot engagement with a crank 51 carried by thereversing shaft 12a. The reversing shaft l2a is provided also with apositioning cam 58 engageable with .a's-pring pressed detent 59, therebyselectively to'maintain the reversing shaft in either its forward or itsrewind position. The pins 48 and. 49 are thus in one end of the slotsiii and 59 for forward operation and in the opposite ends for reverseoperation. In both positions the damping links are normally angularlydisposed with respect to the perpendicular fromthe common. diameter ofthe associated'driVingJand driven disks.

The driving ratio of the transmissionelements 2d and 25 is varied .bymovement. of thecontrol links 42 and 48, respectively, inresponsetomovement of the dancer pulleys 1 andii; respectively. For thispurpose, 1 the dancer, pulleys T1 tandlif are mounted respectively uponarmsB 'andi'fil -extending laterally from apair of rotatable shafts 62and 63, respectively. The .shaftsBZ and 63 are mounted insuitablebearings .(not shown)fand are biased by helical springs I'Bianidi'fif,-respectively, to maintain.tension.onithe wireil. Specifically. theshaft 62. is biased in aicounter'clockwise direction andthe 'shaftL63isTbiase'dfin'a clockwise direction, as viewedat "Fig. :1. The pulley.arms iiilan'dfSl may, if desired, be made of relatively stiff-springmaterial to absorb's hock and thereby addtothestability-Oftheitransmission mechanism. The "shafts"62"and"63"areeach providedatone end with collarsB6andf61, respectively, towhich thebiasin vspringsfiM'and are connected. A. pair of?1inksf68..an'd.69areeccentrically pivoted to "the collars 'f66 "andt'l, respectively, at oneend and have theirothererids pivotally connected to the rockerilevers45and 44, respectively, .at the ends,oppositethecontrol links 42 and 46,respectively.

The idler pulleys 9. and I0. arerotatably mounted upon axiallymovable-and non-rotatable shafts ill and H, respectively,disposedparallel tothe shaft [8. The shafts?!) and H are continuouslyreciprocated by a level winding mechanism 12 driven from the shaft22 by.a wormi'l3 mounted thereon. The worm "l3 meshes with :aworm wheel 14mounted upon .a counterfshaftTEthe other end of whichcarr-iesa spurlgear1B. The spur gear'lt meshes. with a spurgearWl mounted upon a counter.shaft lfiithe other. end of'which carries a bevel gear 7-9. Thebevelggearflfi 00- operates with .abevel geariflil, mountedtupona shaft81 perpendicular. to the shaft'l'S. an'dcarrying at its opposite enda,pairiof.eccentricycam disks 82 and83. "Theldisks82, andifiilperipherally engage a pair .of.level winding leversf84-and 85,1-espectively,,which are mounted .upon'fixed'pivots 86 and 87!,respectively. 'The'movableerfds of" the levers 84 and'B5 engageaxial'slotsinttheishafts if! and H, respectively, andthe'leversarebiasedinto engagement with theperipheryof theidisks 52 and 133, respectively,by helical compression springs 88 and tfi engaging ,collarsiml and! l"on the shafts T0 and ll, respectively. "It will be evident that. as thelovers 84' and"'85*ar e" oscillated by the cam disks their respectiveshaftsarecontinuously reciprocated toeffect level windingpf the wire Iuponthe reels'Z an'cl3. 7

It has been found thatjbecause of friction losses in the'dancer pulleysland B'and'iIrthe recording and erasing heads 4 and 5, respectively,

ciated withthe take-up reel.

the tension on opposite sides of the capstan 6 may be maintained equalonly if the spring tension on the forward dancer pulley is somewhatgreater than that on the trailing dancer. By the forward dancer pulleyis meant that dancer asso- For this purpose, the biasing force exertedby the spring 64 upon the dancer pulley l is adjusted to be greater thanthat exerted by the spring 65 upon the dancer pulley 8, and anadditional spring 92 controlled by the reversing shaft l2a is arrangedto add to the effect of the spring 65 in forward operation when the reel3 is serving as a take-up reel and to exert little or no efiect upon thespring 65 when the reel 2 is serving as a take-up reel in rewindoperation. For this purpose, the spring 92 is connected at one end tothe lower end of the link 69 and at the other end to an arm 63 mountedupon the reversing shaft [2a. The arm 93 is so disposed that, when thereversing shaft is in its forward position, tension is applied to thespring 92, while when the reversing shaft is in its rewind position thespring 92 is substantially untensioned. By this arrangement, it ispossible to maintain the tension on opposite sides of the capstan pulley6 substantially equal, so that there is no tendency for the wire to slipupon the capstan.

With the foregoing understanding of the construction and arrangement ofa wire recording apparatus embodying my invention, the mode of operationof the apparatus will be fully understood from the followingdescription.

Let it first be assumed that the reversing lever I2 is positioned forforward operation, as shown at Fig. 1, so that the wire I is suppliedfrom the reel 2 to the reel 3, passing through first the erasing head 5and then the recording head 4. In this operation, the friction disk I!is driven by the motor l3 in a counterclockwise direction, as indicatedupon the drawing. Also, the damping links 41 and 43 are disposed withtheir lower ends in the right-hand ends of the slots 50 and 5|,respectively. In this position, the pins 48 and 49 are displaced to theright of a perpendicular to the common diameter of the driving anddriven disks. The control links 40 and 42, in the normal mid-position ofthe apparatus shown, are substantially vertical or perpendicular to thecommon diameter.

In the counterclockwise or forward direction of rotation of the disk H,the belt and pulley 2| rotate the disk 23 in a counterclockwisedirection. The capstan pulley 6, being connected directly to the shaftl8, also rotates counterclockwise and in the same direction as the disk23. The variable transmission 24 connecting the disk 23 to the disk 26effects clockwise rotation of the disk 26 and the connected reel 2.Similarly, the variable transmission connecting the disk 23 to the disk21 effects clockwise rotation of the disk 21 and connected reel 3. Bothreels are thus positively connected to be driven in the direction ofwire travel. In the forward direction of operation, the reel 2 serves asa supply reel and the reel 3 functions as a take-up reel. As the Wiretravels from one reel to the other, the level winding mecha nism 12continuously reciprocates the shafts 1i) and H and the connected idlerpulleys 9 and [0, respectively, thereby smoothly to wind the wire uponthe take-up reel.

It is, of course, desirable to maintain the wire tension equal on bothsides of the capstan 6, so that there is no tendency for the wire toslip on the capstan. If the wire has the same desired tension on bothsides of the capstan, and if the reels contain about equal. lengths ofwire Wound thereon, the dancer pulleys 1 and 8 will be maintained insuch positions that the jackshafts 39 and 3! of the variabletransmission mechanisms 24 and 25 lie along the common diameters oftheir associated driving and driven disks. The disks 26 and 2! are thendriven at the same speed as that of the driving disk 23. It is thisposition of the mechanism which has been illustrated at Fig. l and towhich the term normal position in the claims refers. It will be recalledalso that, in order that the wire tension upon opposite sides of thecapstan 6 may be maintained equal, the biasing force on the dancerpulley 8 is greater than that on the dancer 1 in forward operation andless than that on the dancer 1 in reverse operation. As shown on thedrawing, the spring 92 connected to the reversing lever shaft isposttioned to aid the helical spring 65 in biasing the dancer pulley 8for clockwise rotation.

It will of course be understood that the symmetrical positions of thevariable transmission mechanisms 24 and 25 illustrated on the drawingcannot be maintained except for a short interval during the operationwhen the diameter of the wire upon both reels 2 and 3 is approximatelythe same. In operation, the capstan 6 drives the wire I at apredetermined constant linear speed, while the transmission mechanisms24 and control the speeds of the reels 2 and 3, respectively, tomaintain the wire tension constant adj acent the reels as the amount ofwire on the reels changes. Thus as the wire winds up on the takeup reelits speed is gradually reduced, whilethe speed of the supply reel isgradually increased.

Let it be assumed, for example, that the diameter of the coil of wireupon the reel 2 is such that wire is supplied too rapidly from the reel2 and the tension at the dancer pulley I becomes less than apredetermined desired value. In such a case, the dancer pulley 1 moves asmall distance in a counterclockwise direction under the action of itsbiasing spring 64, and the consequent rotation of the crank hub 86 movesthe link 68 downwardly. Thus through the rocker arm 45 the control link42 of the variable transmission 24 is moved upward and the quill 32 ofthis transmission element is rotated about its point of pivotalconnection with the damping link 43. Since the jackshaft 36 is now nolonger diametrically disposed with respect todisks 23 and 26, it hasimparted thereto an axial component of movement. With the frictionroller 35 above the hori zontal diameter of the disk 26, this axialmovement is toward the right as shown in the drawings, or away from thedisk 26 and toward the disk 23. As the jackshaft 31'; moves axially, thedamping link 53 rotates in a clockwise direction about its lower endthereby to raise the friction roller 34 of the transmission 24 and torestore the quill 32 to a horizontal position. Eventually, a newposition of equilibrium is reached in which the jackshaft 36 liesparallel to and above the common diameter of the disks 23 and 26 withthe friction roller 35 spaced from the center of the disk 26 by adistance greater than that between the friction roller 34 and the centerof the disk 23. It is therefore evident that the speed of the disk 2%;will be less than that of the disk 23, and that the speed of the reel 2is thus reduced, thereby to preventfurther decrease in the tension ofthe wire I as it leaves the reel-and to maintain the tensionsubstantially constant within differential limits. I

disk '23.

saeoegees Similarly, few-111 be evident that, if thezreel-fZ isrevolving too slowly, :so that the tension at :the dancer pulley I-increases,lthe dancer .pulley is moved ina' clockwise directiona'thelink68 raised,

and the control l-ink ilis lowered. lWith the friction roller- 35 belowthe horizontal centerlinerof the disk 26, axial movement of theiackshaftfw and below the common diameter of the disks-and the distancebetween the1O116f-35 alld the-center of the disk 26' less than that'betWeen-the'roller "stand the center of the -disk 23. Thusfthe disk 25is driven at "a speed greater than thatf the disk 23, so that wire issupplied from 'the reel 2 at a greater rate, thereby to maintainthe'desired tension within differential limits.

The variable transmission mechanism-25 functions inan entirely similarmanner to control the speed of the'take-upreel 3-in'such away that thetension of the wire between -the "capstan 6 and the reel'3 ismaintaine'd'at the desired value.

In general, therefore,- it 'will' be evident that, at

the beginningof a winding operation, when substantially all thewire ison the supply reel 2" and very little wire upon'the-reel 3,*the "reel 2-is driven more slowly than thedriving disk 23 and the reel 3 -driven-more-rapidly than the driving --As the roll of wire is reduce'dupon thereel 2, the speed of" the "reel gradually increases, and as thewire-builds'np upon the reel 3, the speed 'of the reel=3=graduallydecreases.Throughout the-operation; the linear speed" of the wire I' is maintainedconstantby the 'vviredriving capstan-'6.

Attention is directed to the'factthat the damping links 4| and 43 aredifierentlydisposed in the two transmission mechanisms- 2 land 2 andthat their relative disposition is reversed' uponreversal of the'wi'removement. This-disposition is required by the directions ofaxialmovement required' of the *jackshafts '30 and --3 I in the twotransmission mechanisms. general,- it is to be noted that the dampinglinks 4|"and 43 are so inclined thataxial' movement-of the associatedjackshaft in response to movement of the associated control link is insuch-a direction that the damping link tends to restore the quill 32to ahorizontal position as a resultof' theaxial'movement. For such restoringaction the damping links must always be disposed at such an angle to theconnected jackshaft thatywhen the jackshaft is tilted towardtheperpendicular to the damping link, axial movement of the shaft-wilLtake place in the direction away from the damping link. Specifically, inthe embodimentof the invention shown and 'with the direction of rotationof the parts assumed for forward operation,

it will be noted that the links 42' andll3" are spaced apart farther attheir lower endsthanat their upper ends,while the links" 40 and 4| arespaced closer at theirlower-"ends than-at=their upper ends. Thespacingof the upper ends'of course is 'fixed by pivotakconnec-tion tothe quill 32.

These relations will be clarified byreference to Fig. 3, in-which'I haveshown a line diagram of the linkage shownat Fig. 1. At Fig.:-3,"I haveshown by dotted lines tilted positions of the jackshafts 30 illustratingthe aboverelationforfor-= 8 kwardwire movement. Itwillibeevidentithatthe I same I relation. exists for: reverse wire: movementonly if the damping links .areishifte'd tdthe' opposite. endsof theslots in the. plates53.

:In :order further. to: explain.theitheoreticalre- .lationsi affectingthe operationof myapparatus, :I haveshowni at Fig.4 a line "diagrammfzasimplisfie'd friction transmission similar-tethe-transmiszsionsi24 and'Z 5 described above, but 'in whichithe damping functioniis omitted..'In the arrange- ;ment'shown at.Fig. 4 the jack'shaft3ll iszpivotallymounted at a fixed: point I00. and istaxiallymovable with'respectito itspivot point. .Thefshaftis shown in a tilted position. .l'Ih-edrivingidisk 23 an'dthe driven disk Zlare shown with theirdi-T'IGCtlOI'iS :ofcrotation :as previously assumed. The disks: 23. and52lare in contact with the 1 rollers l34and 35, respectively. Theivelocityof the disk :23: at its point of contact with the: roller 34: is 1illustrated bythe vector V 23; and: the velocity of 5 therdisktfl at itspoint of contact with theroller o35iis2i11115t18id by the: vector V2.7."-The disk 23 therefore tends to impart to the'roller'34 a tan- .gentialvelocity VnT: and an axial velocity Vse i. while thedisk 2ltends toimpart-to the roller 35 :a tangential velocity Van-and an axial velocityVssA. -It will thus be evident that, since the jackshaft 39 is axiallymovable, the shaft and itsconnectedrrollers will move axially in thedirection :indicated toward the-center'of the disk-23 and away from thecenter of the disk-"11. Thus'in the course of'onerevolution,xlthe'pointof contact of the roller 34 with the "disk- 23-w-i1l -f0lloiz/ a spiral :path -I M indicated by dotted lineat Fig. 4.It may bedemonstrated mathematically that the 1 theoretical axial:velocities V34A a11d V35A are not the-same, so thatthere-willinecessarily be some eslight slippage. 7

From Fig. I 4, it' will be evident. that if desired thejackshaft 30 maybe'slidabiy mountedin a .-short'qui1l centrally pivoted-ate fixed-point,rather than being carried on the control and damping-links describedwith reference to Figs. .1 and 3. At'jFig. 5, I have shown a fragmentary.linediagram ofa portionof the apparatus includingone suchquill IE2centrally pivoted atafixed pointzand provided with an-extending=armI02a. Those portions of the apparatus shown at Fig; 5 corresponding tolike elements shown'in the other figures have been assigned the samereference numerals. The mechanism 'of Fig. 5 is'inverted with respect toFig. 1 and-the wire is oppositely wound:on the're'els. This relationshould-be =.rborne"inr mind in noting thecorrespondence of elementsbetween the two-figures. 'lt will' be noted at-Fig. 5 that thequill-102' is shorter than the jackshaft'dfl and thatthejjackshaft 30;is axially movable within the "quill. The dancer pul ley" I of Fig: 5*ismountedupon a; bell crank I 03 which -ispivotally mounted at afixed.point I04 and connected tothe. jackshaft'arm 192a by -a'link I05. Thedancer pulley is biased by means ofa spring Hit in a directionto:.apply.tension to the .wire I. The jackshaft 30 is shown tilte'd atanangle a with: respect. to the common diagonal "thIOUghthediSksZS' and 26and displaced a;dis .tancem from its mid-position inthe quill l 02. I It.will be understood .thatthe .',tilting of .the jackshaft atv the anglea. results from liftingofithe 'dancer pulley? throughadistance y; fromits position when the jackshaft is horizontahand that the axial movement,of the 'jackshaft =through the distance a: arises" from its tiltingasexplained'with respect to Fig. 4.

It'may-"be 'demonstrated by the equations of motion that, for themechanism shown at Fig. 5, the axial velocity or the jackshaft 30 is afunction of the distance 1 only, and that, because of the speed changesin the disks effected by the axial movement, simple harmonic axialoscillation of the jackshaft will result. In order to effect damping ofsuch oscillations, it is necessary to introduce into the axial velocityof the jackshaft a function of the displacement at. This isaccomplishedby the damping links M and 43 previously described. As willnow be evident, these damping links have the effect of reducing theangle a and thereby reducing the axial velocity of the jackshaft as thedisplacement :1; increases and without affecting the displacement g. Itwill be evident that other suitable damping mechanisms may be utilizedto accomplish this purpose within the scope of my invention.

At Fig. 6, I have shown a further embodiment of my invention having acontrol and damping linkage similar to that of Fig. l and includingadditionally mechanisms for braking the reel when the wire is slack,such as in th event of Wire breakage or when the wire is changed. Thoseelements of Fig. 6 corresponding to like elements of Fig. 1 have beenassigned the same reference numerals. In noting the correspondence ofparts in the two figures, itshould be observed that the pulleyorientation of Fig. 6 is reversedvvith respect to Fig. 1 and the wire isoppositely wound on the reel. At Fig. 6, the dancer pulleys I and 8 aremounted upon pivoted arms 60 and BI and biased by springs 64 and 65,respectively, as at Fig. l and links 68 and 69 connect the arms 60 andEl with the leaves 55 and M3, respectively. At Fig. 6, however, Iprovide also apair of brake shoes Ill! and I Elli pivotally mounted uponfixed pivots Hi9 and Ill) and arranged toengage the driven disks 2! and26, respectively. If desired, of course, the brake shoes may engage thereels directly or may engage separate brake drums on the reel shaft. Thebrake shoes are actuated by links HI and H2 connecting the shoes toextensions on the dancer pulley levers BI and 69, respectively. Thus ifthe wire breaks or becomes slack for any reason, the brakes will comeinto action. Preferably, the brakes have a differential action, so thatmore brakingis obtained upon any reel when it is turning in a directionto unwind the wire. Thus, the supply or trailing reel is braked the mostso that the wire is kept taut. The brakes will ordinarily come intoaction only when the wire is changed and if the initial position of therollers is 'incorrect for the diameters of the new reels. Thebrake onthe delivery reel will then check the rotation of the reel during thefirst two or three turns until equilibrium is established.

While I have described only certain preferred embodiments. of myinvention by way of illustration, many modifications will occur to thoseskilled in the art and therefore, it is intended that the inventionshould not be limited except as defined by the following claims.

What I claim a new and desire to secure by Letters Patent of the UnitedStates is:

1. In a tension control system for a traveling strip of material, a pairof spaced reels, constant speed driving means engaging said strip in--termediate said reels, a driving disk, a driven. disk connected to eachsaid reel and positioned in the plane f said driving disk, a pair ofaxially movable jackshafts each carrying at one end a friction rollerengaging said driving disk and ally movable jackshaftseach carrying atone end a friction roller engaging said driving disk and at the otherend a friction roller engaging one of said driven disks, separate meansresponsive to the tension of said strip between each said reel and saidstrip driving means for tilting the associated jackshaft with respect tothe common diameter of its driving and driven disks thereby to effectaxial movement of said jackshaft, and separate means responsive to axialmovement of said jackshafts for restoring the associate-d jackshaft to aposition substantially parallel to said common diameter.

3. In a tension control system for a traveling strip of material, a pairof spaced reels, constant speed driving means engaging said stripintermediate said reels, a driving disk, a driven disk connected to eachsaid reel and positioned in the plane of said driving disk, a pair ofaxially movable friction spools each engaging said driving disk and oneof said driven disks and being normally disposed with their axessubstantially parallel to the common diameter of the associated drivingand driven disks, separate means responsive to the tension of said stripbetween each said reel and said strip driving means for tilting theassociated friction spool with respect to said common diameter therebyto effect axial movement of said spools and change the driving ratio ofsaid disks, and separate means responsive to axial movement of saidspools for controlling the angle of tilt of the associated spool toprevent hunting thereof.

4-. In a tension contro1 system for a traveling strip of material, apair of spaced reels, means engaging said strip intermediate said reelsfor driving said strip at a predetermined linear speed, a driving disk,a driven disk connected to each said reel and positioned in the plane ofsaid driving disk, a pair of jackshafts each carrying at one end aroller engaging said driving disk and at the other end a roller engagingone of said driven disks, a pair of parallel pivoted links eachsupporting oneend f one of said jackshafts in a normal positionsubstantially parallel to the common diameter of the associated drivingand driven disks, and separate means controlled by the tension of saidstrip between each said reel and said strip driving means for tiltingthe associated jackshaft about said supporting link thereby to effectaxialmovement f the shaft, said supporting links being normallyangularly disposed with respectto said common diameters thereby toeffect restoring movement of said jackshafts toward said normal positionin. response to axial movement thereof.

5. In a tension control system for a traveling strip of material, a pairof spaced reels, constant speed driving means engaging said materialintermediate said reels, a driving disk,a driven disk connected to eachsaid reel and positioned in the plane of said driving disk, a pair ofjackshafts each carrying at one end a friction roller enagingsaiddriving. disk. and at the .opposite end a friction roller engagingone-ofsaid driven disks, a pairof 'quills inwhich said jackshaft's aremounted,a pair of pivoted links .supporting each said quill in' a normalposition. parallel'to the common diameter of the associatedldriving anddriven disks, and meansincludingone link of "each said pair of links andresponsiveto. the tension. of said strip between. each. said. reel andsaid strip drivingmeans fortilting the associated quill. with respect tosaid. common diameter thereby to efiect axial movement of the associatedjackshaft; the other link of each saidIpair of links. being disposed to.restore the connected quilljto parallel relation with said.commonldiameter "response to said -axial movement.

6;A- constantfltension' control system for a travelingstrip' of"material comprisingv a. reel, a driven"disk.'connected to said reel, adriving disk' in: theplane' ofsaidfdr'iven disk a .jacksh'aftcarryin'gat' one end'a .friction rollerengaging. said driven disk''and'iatth other end a friction. roller engaging 'saiddrivingdisk,--means normally supporting. said jackshaftin substantially parallel'relation 'withthe 'common .diameterof said disks, and means responsivetohthetensionlof saidstrip for tilting. said 'jacksha-ft'witl'i -respectto' said' commondiam'eter thereby. to effect axial movement of Isaid'jacksh'aft and to change. the.

driving ratio between said 'dis'ks.

'IJA constant: tension. control system. for a traveling" strip ofmaterial comprising. ,aireel, a driven disk connected to.said reel,iadriving disk.

in the'plane of Lsaididriven disk, a..friction spool,-

means. normally supporting; said I spool in. substantially parallelrelation with. the. common. di.-- ameter'offsaid. disks with opposite.endslof .said spool engagingsaid driving. .andld-riven disks .re=-

spectively means responsive to. thehtension. of said strip for tiltingsaidJspool liwith .respect to said common' diameter thereby to.effctaxial movement "of"said."sp ool and Ito. changethe-driving; ratiobetweensaidfdis'ks, and. dampingv means comprising means responsive-tosaid 'axial movement'for restoring saidspool to itsunormal pare allel.relation with" resp'ectlto.saidcommon diameter:

8'; A" constant" tension control systmior a. travelingstrip of .material'compris'ing a reel, a driven disk connected 'to saidreel; a-dlivingdisk. in the-plane -of' said" driven. disk, ,a. friction spool havingopposite ends engaging said driving and driven "disks respectively,means including a pivoted link normally having an angular-- relation.

with"1'espect"to1the common diametenof-said.

disk' for supporting said? spool Lin a-normal .position" With'iits axissubstantially... parallelLto .said common diameter; means responsive.tontheztem sion'of'said strip?for'tilting'theaxis of said. spook v aboutsaid link thereby to efie'ct axial movementof said'spool, said: linkrestoring .theparallel re..-.

latiombetween'lthe axis 1 of "said? spool and said;

common diameter" in response. to. said. axial movement:

9: A constant .ten'sion' system ion a. traveling strip of materialcomprising azreel; aldrivendisk connected;to-saidreel, a driving diskinthe :planev is mounted; a' air of "links pivotally connected. toopposite 'ends'o said' quill and pivotally mounted to supportsaidquillin a normallposition. par

allel' to-"the com on diameter. of said disks said T linksebeingangularly disposed with respect to each other. and .one of said-links.being normally substantially,perpendicular to said common diameter, andmeans including said perpendicular link'. and responsive to-. thetension of-said strip forztilting saidiquill about thenother of saidlinks thereby. lto..eifect.axial-movement of said jackshaft'... I

10. .A .constanttension. control system for a traveling, strip ofmaterialcomprising a reel,- a driven .diskiconnectedc-to said reel, a.driving disk inatheeplane of said v driven disk, a jackshaft carrying=at. oneeend a. friction. roller engaging saidldriven disk and-.-at the'other end a friction roller:engagingsaiddfiving -disk,.a quill in whichsaidjackshaftis mounted. a. pair of supporting linksivotallytconnectedto opposite ends of said quill and pivotallymounted.to support said quill in.a..normal position substantially parallel tothe common. diameter .otsaid .d-isks, said links being angularlydisposedwith respect to each other and one. ofsaidlinks being-normallysubstantially perpendicular.to..said..common diameter, means includingsaid perpendicularlink and responsive to theatensionaofsaid. strip fortilting said jackshaft'abouttheother ofsaid links thereby to eifect.axial..movement of said jackshaft and to change. thevdriving: ratiobetween said disks, means for. reversing the. direction of rotation ofsaiddriving disk, andmeansassociated with said reversing meansfor-reversing the angular relation of.said.links saidaangularly disposedlinks being-arranged .in either directionof rotation of said diskstorestorertheparallel relation between saidjackshaft .and: said. common.diameter in responseito axial .movement'of said jackshaft.

11.1A.constant.tension control system for a travelingstrip{.of-..materialcomprising a reel, a driven .diskkconnectedtosaidreel, a driving disk in. theplane .of said driven. disk, meansassociated with said.driving,.disk.,andengaging said strip for drivingsaid strip at apredetermined linear speed, a jack'shaft carryingat 'oneend a friction roller engaging,..saidldriventdisk and at the other end africtionroller:engagingsaiddriving disk, mean normally(supporting. said.jackshaft in substantially .parallel relationwith. the common diameterof .Tsaidcdis'ks,Landlmeans responsive to the tension of Jsaid.strip..for tilting; said jackshaft with respect .to saidcommondiametertherebyto effect axialf'movement 'of fsaid'jackshaft and to change thedr'ivingratio .between. said disks.

12'. In. atension .control .system fora traveling strip'oflImateriaLfa.pair. of spaced reels, means intermediate. saidree1s..for. driving saidstrip at a. predetermined. lineanspeed, means for driving both saidreels inthedirection. of travel of said strip;,sep,arate meansresponsiveto the tension of said strip between each said reel and said stripdriving means .ior controlling the speed of the associated reel,.andfmeansactuated by said tension responsivemeansiorbraking-said reelsupon apredetrminedldecrease in the tensionof said strip.

13'. In a tensioncontrol-system for a traveling strip,.of.lmaterial, ,a.pair of..spaced .reels, means intermediate said-.reels. for driving saidstrip at a predetermined linear speed, means for driving both'said.reelsin thedirection of travel of said strip, .separate..meansresponsive to the tension ofsaidstriploetween each said reel and saidstrip driving-meansfor.control1ing the speed of the associated reel,difierential braking means associatediwith each said reel andarranged toapply to each reel aibraking force greater in the direc- 13 tion ofunwinding of said strip than in the direction of Winding, and meansresponsive to a predetermined decrease in the tension or said strip foractuating said braking means.

14. A reeling apparatus comprising a pair of spaced reel carrying anelongated strip of material, a driving capstan engaging said stripintermediate said reels, operating means slidably engaging said stripadjacent said capstan, a pair of dancer pulleys engaging said strip andpositioned to include said capstan and said operating meanstherebetween, means for applying to said dancer pulleys fixed biasingforces of unequal value, means for reversing said capstan, and

means controlled by said reversing means for superposing an additionalbia upon the dancer pulley having the smallest fixed bias.

15. A reeling apparatus comprising a pair of spaced reels carrying anelongated strip of Ina-- terial, a driving capstan engaging said stripintermediate said reels, operating means slidably engaging said stripadjacent said capstan, a pair of dancer pulleys engaging said strip andpositioned to include said capstan and said operating meanstherebetween, spring means for applying to said dancer pulleys fixedbiasing forces of unequal value, means for reversing said capstan, andadditional spring means controlled by said reversing means forincreasing the bias of the dancer pulley having the smallest fixed biasto a value greater than the larger fixed bias by approximately thediiference between said fixed biasing forces.

16. A reeling apparatus comprising a pair of spaced reels carrying anelongated strip of material, a driving capstan engaging said stripintermediate said reels, means for driving either of said reels as atake-up reel, operating means slidably engaging said strip adjacent saidcapstan, a pair of dancer pulleys engaging said strip and positioned toinclude said capstan and said operating means therebetween, spring meansfor applying to said dancer pulleys fixed biasing forces of unequalvalue, means for reversing said capstan, and additional spring meanscontrolled by said reversing means for increasing the bias of the dancerpulley having the smallest fixed bias by approximately twice thedifference between said fixed biasing forces, said reversing ing anelongated magnetic record medium, a

driving capstan engaging said record medium intermediate said reels,means for driving either of said reels as a take-up reel, a magneticoperating head frictionally engaging said record medium adjacent saidcapstan, a pair of dancer pulleys engaging said record medium andpositioned to include said capstan and said operating head therebetween,spring means for applying to said dancer pulleys fixed biasing forces ofunequal value, additional spring means having a disabled position and aposition for superposing upon the smaller of said biasing forces anadditional bias equal approximately to twice the diiference between saidfixed biasing forces, means for reversing said capstan, and meanscontrolled by said reversing means for positioning said additionalspring means always to maintain the larger net bias upon the dancerpulley adjacent the takeup reel.

ARTHUR W. SEAR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date 839,261 Braud et a1 Dec. 25, 19061,406,665 Ljungstrom Feb. 14, 1922 1,520,546 Murray Dec. 23, 19241,700,981 Hayes Feb. 5, 1929 1,865,410 Byles June 28, 1932 2,012,208Wildy Aug. 20, 1935 2,304,913 Herzig Dec. 15, 1942 2,328,322 BertholdAug. 31, 1943 2,338,605 Tuttle et a1 Jan. 4, 1944 2,462,558 Scheuermannet a1. Feb. 22, 1949 FOREIGN PATENTS Number Country Date 568,627 FranceDec. 24, 1923 587,628 France Jan. 20, 1925

